There are numerous prior art devices for exposure counter controls within cameras. Among these prior art devices are exposure counter controls that are integrated with the film loading mechanisms of cameras. A typical, and desirable, feature of a exposure counter within a camera design is that the mechanism can differentiate between the condition film being present within the camera and the condition where film is not present within the camera. A further refinement of the film presence feature is that of detecting when a film cartridge has been loaded in the camera but the film still remains within the film cartridge and that condition where the camera has been initialized with the film advanced out of the film cartridge to its first metered position.
In the condition where the film is still within the cartridge, the exposure counter control must not allow the user to attempt to take a picture. This feature is conventionally provided within prior art devices by a mechanism employing a sprocket to sense perforations in the film. There is a shortcoming within the prior art in attempting to provide the features of sensing whether the film has been advanced to its first metered position without the use of a sprocket in the camera exposure counter control. The inclusion of a sprocket within the design of a camera increases size and part count and alternative methods that do not require a sprocket are, therefore, desirable.
From the foregoing discussion it should be apparent that there remains a need within the art of exposure counter controls for camera design that integrates the features of detecting when the film has been loaded and advanced to its first metered position without requiring a sprocket in the design.